Enhanced Charge Transport via Metallic 1T Phase Transition Metal Dichalcogenides-Mediated Hole Transport Layer Engineering for Perovskite Solar Cells

In perovskite photovoltaic cells having a p-i-n structure, the hole transport layer (HTL) plays an important role in device performance because it has a direct impact on the crystallinity of overlying perovskite films as well as the interfacial charge transport. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT : PSS) has been widely used as an HTL owing to its desirable electrical and optical properties with solution processability. However, improving the functionality of PEDOT : PSS still requires broad attention to maximize the related solar cell performance, such as further enhancing the electrical properties to achieve better charge transport at the electrode and photoactive layer interface and reducing the nucleation energy barrier to improve crystallinity of the overlying perovskite films. Two-dimensional transition metal dichalcogenides (TMDs) have been studied in various optoelectronic devices owing to their intriguing optoelectric features. In this study, tungsten diselenide (WSe2) was implemented with PEDOT : PSS to enhance the performance in p-i-n perovskite solar cells. The incorporation of WSe2 into PEDOT : PSS led to improved charge transport at the photoactive layer and electrode interface as well as the favorable growth of the perovskite crystal. As a result, a notable improvement in the performance of the solar cell having the WSe2-mediated PEDOT : PSS HTL was observed in comparison to that of the PEDOT : PSS only device, which had power conversion efficiencies of 16.3% and 13.8%, respectively. The facile approach proposed in this study may be readily extended to various other perovskite-based optoelectronic devices beyond solar cells toward the enhancement of device functionality.